Method of controlling an electro-magnetic molten metal pouring device

ABSTRACT

Described is a method of controlling an electro-magnetic molten metal pouring device which comprises an electro-magnetic pump which is adapted to generate a traveling magnetic field by a.c. excitation thereby to impart impellent force to molten metal present inside the pump, a molten metal reservoir located on one side of the pump, and a nozzle positioned on the other side of the pump; wherein supplying of molten metal to the molten metal reservoir is started and stopped respectively by detecting the lower limit level and the upper limit level of molten metal present in the molten metal reservoir, and pouring of the molten metal into a mold is started and stopped respectively by detecting the arrival of the mold and the molten metal fullness in the mold. In addition, disclosed is a method of controlling a molten metal pouring operation; wherein the final exciting voltage of said electro-magnetic pump in the preceding molten metal pouring operation is memorized, and the exciting voltage thereof is gradually raised up for a subsequent molten metal pouring operation, said memorized final exciting voltage in the preceding molten metal pouring operation being regarded as the initial exciting voltage for the subsequent molten metal pouring operation.

United States Patent 91 Yamada et a1.

[ Feb. 12, 1974 METHOD OF CONTROLLING AN ELECTRO-MAGNETIC MOLTEN META POURING DEVICE [73] Assignee: Kabushiki Kaisha Yaskawa Denki Seisakusho, Fukuoka-ken, Japan 22 Filed: Dec. 14, 1970 21 Appl. No.: 97,752

[58] Field of Search..... 164/155, 156, 49, 147, 133; 222/1; 417/50 [56] 7 References Cited UNITED STATES PATENTS 3,122,800 3/1964 Naffziger 164/155 3,441,261 4/1969 Sommer 164/155 X 3,534,886 10/1970 Von Starck... 222/1 3,515,898 6/1970 Von Starck 417/50 X Primary Examiner-Robert D. Baldwin Attorney, Agent, or Firm-Fitzpatrick, Cella, Harper & Scinto f [5 7 ABSTRACT Described is a method of controlling an electromagnetic molten metal pouring device which comprises an electro-magnetic pump which is adapted to generate a traveling magnetic field by ac. excitation thereby to impart impellent force to molten metal present inside the pump, a molten metal reservoir located on one side of the pump, and a nozzle positioned on the other side of the pump; wherein supplying of molten metal to the molten metal reservoir is started and stopped respectively by detecting the lower limit level and the upper limit level of molten metal present in the molten metal reservoir, and pouring of the molten metal into a mold is started and stopped respectively by detecting the arrival of the mold and the molten metal fullness in the mold. In addition, disclosed is a method of controlling a molten metal pouring operation; wherein the final exciting voltage of said electro-magnetic pump in the preceding molten metal pouring operation is memorized, and the exciting voltage thereof is gradually raised up for a subsequent molten metal pouring operation, said memorized final exciting voltage in the preceding molten metal pouring operation being regarded as the initial exciting voltage for the subsequent molten metal pouring operation.

2 Claims, 6 Drawing Figures PAT-ENTEUFEBI 21974 3,791,437

' SHEEI 1 or 2 UNNVWN'NU'V'NNW" METHOD OF CONTROLLING AN ELECTRO-MAGNETIC MOLTEN METAL POURING DEVICE BACKGROUND OF THE INVENTION In general, a casting work is conducted in a poor working circumference such as a poor environmental atmosphere, a high-temperature, etc. Therefore, au-

tomatization and more particularly speed-up are essentially required in the field of the casting work. However, it is very hard to control the molten metal pouring operation whereby the automatization still falls behind.

'In the automatization, it may be taken into consideration to successively attain a control from a metal melting furnace to a molten metal pouring device. However, if the relationships between the fact that molten metal is intermittently furnished out of the metal melting furnace and a flow of a conveyer carrying molds thereon, are taken into account, a flow rate of molten metal is not always stable and therefore the yield of production may be lowered. Moreover, the output of an electro-magnetic pump is required to be varied over a considerable wide range thereof.

In addition, controlling of molten metal by means of the electro-magnetic pump is useful because it makes the automatic operation possible. However, in the case where a certain amount of molten metal is supplied to the molten metal reservoir from the metal melting furnace and the thus supplied molten metal is successively poured into molds, said controlling method is disadvantageous because the molten metal level is successively varied in the molten metal reservoir whereby the molten metal pouring rate becomes unstable.

SUMMARY OF THE INVENTION It is, therefore, a primary object of the present invention to provide a method of controlling an electromagnetic molten metal pouring device readily operable, wherein supplying of molten metal into a molten metal reservoir is roughlycontrolled by detecting the molten metal level of the molten metal reservoir and an electro-magnetic pump is controlled by detecting the position of a mold and the fullness of molten metal in the mold, on the mold side.

Another object of the present invention is to provide a method of controlling an electro-magnetic molten metal pouring device, wherein supplying of molten metal to a molten metal reservoir and pouring of molten metal into a mold are individually controlled and the whole control is simple.

Further object of the present invention is to provide a method of controlling an electro-magnetic molten metal pouring device, in which an electro-magnetic pump is employed which generates a substantially constant impellent force because the flow of molten metal is stable and smooth.

Still further object of the present invention is to provide a method of controlling an electro-magnetic molten metal pouring device, wherein molten metal is poured at a constant or required flow-rate by gradually .raising the exciting voltage of an electro-magnetic pump, with preferable relative control on successive stages.

- BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawings:

FIG. 1 is a cross-sectional view of an electromagnetic molten metal pouring device employed in this invention;

FIG. 2 is a plan view of a longitudinally sectioned electro-magnetic molten metal pouring device;

FIG. 3 is a side view of an electro-magnetic pump being used in an embodiment of FIG. 1;

FIG. 4 illustrates the arrangement of devices employed for the present invention;

FIG. 5 is a block diagramatic view illustrating a control method of an embodiment according to the present invention; and

FIG. 6 exhibits a graphic diagram showing the change of the exciting voltage of an electro-magnetic pump employed for the embodiment shown in FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION With reference now to the accompanying drawings and more particularly to FIG. 4; there is described an arrangement of the device which comprises a metal melting furnace A, a trough B, a molten metal storing furnace C equipped with a means D for keeping warmth such as an induction coil, a molten metal pouring device E, a mold F, a level detector G, such as a float switch adapted to detect a molten metal level of a molten metal reservoir 1, a fullness detector H which is to detect the fullness of molten metal inthe mold, and a conveyer J conveying the mold successively. As apparent from FIGS. 1 and 2, the molten metal pouring device comprises the molten metal reservoir 1 and a molten metal passage 2 located next to the reservoir 1. The larger part of the molten metal passage 2 is substantially horizontal below the molten metal lower limit level of the molten metal reservoir 1. An electromagnetic pump 3 is so arranged as to accomodate the molten metal passage 2 therein. As shown in FIG. 3, the electro-magnetic pump of a laminated iron core 31 is provided with a number of .slots 33 in which windings 32 of phases U, V, and W are inserted respectively, and a traveling magnetic field moving along the air-gap surface of the iron core is generated by ac. excitation thereby to impart impellent force to the molten metal present in the molten metal passage 2. A nozzle 4 is communicated with the molten metal passage 2, and is extended, starting from a position higher than the molten metal upper limit level H with a slightly rising gradient, and further hasa molten metal pouring outlet 5 at its end portion. The impellent force directed from the molten metal reservoir 1 to the nozzle 4 is imparted to molten metal present in the molten metal passage 2 by the excitation of the electro-magnetic pump 3, whereby the molten metal climbs up into the nozzle 4 and then flows down into the mold F through the pouring outlet 5. When the mold F is filled up with a required quantity of molten metal, the fullness detector H starts to work thereby to remove the excitation of the electromagnetic pump 3 so that the molten metal present in the nozzle 4 immediately flows back into the molten metal passage 2: to stop pouring of the molten metal. At the same time, a signal is supplied to the conveyer so as to shift the mold.

Molten metal in the metal melting furnace A is transferred to the molten metal storing furnace C through the trough B. When the molten metal surface in the molten metal reservoir 1 is lowered to reach the lower limit level L, the detector G operates to tilt the molten metal storing furnace thereby to supply the molten metal. When the molten metal surface reaches the upper limit level H, the detector G furnishes a signal so as to stop tilting of the molten metal storing furnace C thereby to stop supplying of the molten metal. Thus, the supply of the molten metal from the molten metal storing furnace C is controlled by the signal furnished from the level detector G, substantially irrespective of pouring of the molten metal into the mold, and therefore accurate control is not necessary. By providing a sufficiently large area for the molten metal reservoir 1, the impellent force generated by the electro-magnetic pump 3 is not influenced by the variation of the molten metal level. When it is detected that the mold is at a predetermined position, the electro-magnetic pump 3 is excited, and when mold is fully filled with molten metal, the excitation of the electro-magnetic pump 3 is removed. If all the molds are equal, it is not required to adjust the excitation intensity. Thus, casting can be accomplished with accuracy at all times. If the molds are different from each other in size, the excitation may be adjusted. ln stopping the pouring of molten metal, if the electro-magnetic pump 3 is excited reversely thereby to impart the impellent force of a reverse direction to the molten metal, it can be accomplished more quickly and effectively to stop the flow-out of molten metal.

Now, with reference to FIG. 5, an embodiment according to the present invention is described as follows:

A molten metal pouring device 6 comprises an electro-magnetic pump 7 located in the middle portion thereof, a molten metal reservoir 8 arranged on one side of the pump 7 and a molten metal pouring trough 9 located on the other side of the pump, both the molten metal reservoir 8 and the molten metal pouring trough 9 are communicated with each other. In the electro-magnetic pump, flat iron cores are provided on both sides (or one side) of a pipe which is small in width and is made of heat-resisting material, the iron cores oppositely positioned are wound with polyphase a.c. windings, whereby a traveling magnetic field moving in an axial direction of the pipe is generated by excitation thereby to impart the impellent force in a magnetic field traveling direction to the molten metal present in the pipe. The molten'metal reservoir is so formed that its lowest level of molten metal is higher than the electro-magnetic pump 7 and its area is large so as to minimize the variation of the molten metal level which may be caused by pouring of the molten metal. The molten metal pouring trough 9 is substantially the same in a cross-sectional area as the pipe of the electromagnetic pump 7 and has a gradient toward its end, and further is provided with a nozzle 10 at a position higher than the highest level of a molten metal of the molten metal reservoir 8.

Accordingly, the electro-magnetic pump 7 is filled with molten metal at all times and the molten metal in the pipe is expelled out of the nozzle 10 by excitation. It is accomplished by operating a regulator 11, a pilot motor 12 thereof, and a switch 13, to excite the electromagnetic pump, to remove the excitation thereof, and to adjust exciting voltages.

In addition, molten metal is supplied to the molten metal reservoir 8 from a metal melting furnace or an intermediary molten metal storing furnace (both not shown).

When it is detected that a predetermined mold is brought to a predetermined position, the switch 13 is turned on by a start signal of pouring thereby to excite the electro-magnetic pump 7. At the same time, molten metal is pushed out of the nozzle into the mold. However, the molten metal surface level is lowered in the moltal metal reservoir 8 as the pouring of molten metal is continued on, and therefore the regulator 11 is operated by driving the pilot motor 12, thereby to gradually raise an exciting voltage of the electro-magnetic pump 7 so that molten metal be poured at a substantially constant flow-rate. When the mold is filled up, the switch 13 is turned off to stop pouring of the molten metal, but the pilot motor is left as it is.

When a mold has been moved out and another mold to be filled with molten metal subsequently is brought in to a predetermined position therefor, the start signal for pouring of the molten metal is furnished thereby to turn on the switch 13 and at the same time to rotate the pilot motor 12, whereby the exciting voltage of the electro-magnetic pump 7 is gradually raised up to pour the molten metal into the mold. When the molten metal level reaches the lower limit level (I) in the molten metal reservoir 8 after the molten metal has been thus successively poured out, the switch 13 is turned off and the pilot motor 12 is reset back to its beginning conditions so that the molten metal can be supplied from the metal melting furnace on the intermediary molten metal storing furnace into the molten metal reservoir 8 up to the upper limit level (h), so as to be ready for the next molten metal pouring operation. In other words as illustrated in FIG. 6, pouring of the molten metal is effected by controlling the exciting voltage to gradually raise the exciting voltage in continuous fashion during the pouring of each mold, and setting the initial exciting voltage for each new mold pour of the operation equal to the final exciting voltage of the last preceding mold pour of the operation. It can be easily accomplished by increasing a voltage raising rate, that is, a revolution speed of the pilot motor 12 to increase the flow-rate of molten metal in the molten metal pouring operation, and the flow-rate of molten metal also can be adjusted with ease.

The exciting voltage may be controlled by utilizing not only a regulator but also a static type means such as a thyristor, and by any other various methods. In addition, during a period when the molten metal is not being poured, the electro-magnetic pump may be excited at a low voltage for keeping warmth of the molten metal.

It is intended, therefore, that all matter contained in the foregoing description and in the drawings shall be interpreted only as an illustrative not as limitation of the invention.

We claim:

1. A method of controlling an electro-magnetic molten metal pouring device comprising the steps of detecting the lower limit level of molten metal in a molten metal reservoir of sufficient size to support a pouring operation of successive molds, supplying molten metal from a molten metal storing furnace to said reservoir when said lower limit level is detected, detecting the upper limit level of molten metal in said molten metal reservoir, terminating the supplying of molten metal from said molten metal storing furnace when said upper limit level is detected, exciting an electromagnetic pump interposed between said molten metal reservoirand a pouring trough having a nozzle to move molten metal from said reservoir into said successive molds, controlling the exciting voltage to gradually raise the exciting voltage in continuous fashion during the pouring of each mold, setting the initial exciting voltage for each new mold pour of said operation equal to the final exciting voltage of the last preceding mold pour of said operation, and resetting the exciting voltage to its inital value for a subsequent pouring operasaid nozzle. 

1. A method of controlling an electro-magnetic molten metal pouring device comprising the steps of detecting the lower limit level of molten metal in a molten metal reservoir of sufficient size to support a pouring operation of successive molds, supplying molten metal from a molten metal storing furnace to said reservoir when said lower limit level is detected, detecting the upper limit level of molten metal in said molten metal reservoir, terminating the supplying of molten metal from said molten metal storing furnace when said upper limit level is detected, exciting an electro-magnetic pump interposed between said molten metal reservoir and a pouring trough having a nozzle to move molten metal from said reservoir into said successive molds, controlling the exciting voltage to gradually raise the exciting voltage in continuous fashion during the pouring of each mold, setting the initial exciting voltage for each new mold pour of said operation equal to the final exciting voltage of the last preceding mold pour of said operation, and resetting the exciting voltage to its inital value for a subsequent pouring operation when said molten metal reservoir is subsequently again filled to its upper limit.
 2. A method according to claim 1, further comprising the step of exciting said electro-magnetic pump during the time between the pouring of successive molds at a voltage mErely sufficient to keep said molten metal warm, but not to cause said molten metal to flow from said nozzle. 